Chromatography Forum

We are using a agilent molecular sieve 5A column to separate permanent gases. It all of a sudden stopped separating the gases...they now appear as one large peak. I noticed that the traps for O2 and mositure were a little saturated so i changed the traps and ran again. The same issue occured. We then baked the column at 190 degress for 1.5 hour again ...same issue occured!. So we thought the column is screwed!...so i changed the column and ran again and the same issue is occuring...peaks are not separating...any ideas?

Also i forgot to add we are using a refinery gas analyzer...with valve switching etc

seamoro,

Have you verified you have flow through the column/detector? Have you verified the injection valve is turning? Have you verified the column switching valves are turning? Not just air moving but the actual valve moving.

Best regards,

AICMM

seamoro,

The bake-out temperature is insufficient. For 1/16” columns, bake out at 250C for four hours. For 1/8” columns, bake out at 300C for four hours. Make sure there is nothing else in the temperature zone that can be harmed by the bake-out temperature. If there is, then either the MS5A must be removed for bake-out, or the components with lower temperature limits must be removed for the mole sieve bake-out. In general, our company places mole sieves in separate temperature zones with other columns that can be heated to 250C or 300C.

Jed Sullenger

Are you using MS-5A column with back flush ?. Looks like your valve timings have been changed, either your sampling valve timing is off in the event table or has a wrong value. Try increasing the sampling valve timing and see. If you have a valve diagram with you then it is easy to trouble shoot the problem. Also the snapshot of chromatograph gives you most of the answers. Since both information are missing in your case ---


regards,

FUR

FUR208 is right


Write more informations about your pneumatic system. What kind of column you use, packed or not? Did you verify if flow rates and temperatures of your unit are proper?


BR

iiYama